In a conventional type of cordless telephone system based on a time division system, synchronism of communication frame is established by means of transaction of synchronizing request code (SYNC code). When terminating a call while synchronism is established, a station hoping to terminate a call sends communication end request code (END code) specified times (for instance, three times) to a called station and terminates communication of the station. On the other hand, the called station receiving the END code recognizes end of communication and terminates communication of the station.
In the conventional type of cordless telephone system, however, a station hoping to terminate communication sends the END code and then terminates communication without checking whether the called station has received the END code. For this reason in a case where the END code has not been received by the called station due to, for instance, interference among radio zones, the called station determines that the radio link had been disconnected for some reason or other, and sends a SYNC code to establish synchronism again, so that synchronism between the station and the called station is again established and communication is enabled. In other words, even if a user wants to terminate a call, a communication call is not disconnected immediately, and transmission continues despite that the station is not used. Such disadvantages to a user as accounting of telephone fee or waste of electric power occur.
As shown in FIG. 8, assume that a calling station A sends the END code 3 times and then enters an asynchronous state (terminates communication), but a called station B does not receive END code, so that the called station B determines that the radio link has been disconnected for some reason or other and continues to send SYNC code until synchronism is established again. The calling station A, receiving this SYNC code, again establishes synchronism and enables communication as in a case where a new request for event is issued.
On the other hand, in the conventional type of cordless telephone system, it is possible to evade the case where a called station can not detect end of communication and synchronism is again established to enable communication. This occurs by employing a system in which a calling station sends the END code and terminates communication only when the calling station confirms that the called station has received the END code, but the telephone line is not disconnected in spite that the user hopes to terminate the call. A state where transmission continues, even though the calling station is not in use, continues for a long time. This creates disadvantages to users such as accounting of telephone fee or waste of electric power.